The present invention relates to a controllable helium-II phase separator, in which superfluid helium-II flows, utilizing the cut-off action of the thermomechanical effect, through at least one capillary gap-shaped canal, the geometry of which can be varied for throughput control by means of at least one control element.
Such a phase separator is known from DE-AS No. 28 06 829 as well as from Research Report BFMT-FB No. 79/47 "Phase Separation of Helium-II in the Weightless State" by Denner et al., FU Berlin. This phase separator consists of a so-called ring gap valve, in which a cylindrical valve element opposite the valve sleeve has a passage gap with a gap width of less than 10 .mu.m and wherein the gap length is varied by axially moving the valve element relative to the valve bushing. In such a phase separator, the cylindrical surfaces of the valve element and the sleeve must be machined highly precisely and be aligned coaxially by means of a separate guide; in addition, the coefficients of expansion of the materials must be matched to each other perfectly, since otherwise there is danger of jamming because of the small gap width. Furthermore, an additional valve or at least additional sealing surfaces at the valve element and at the valve sleeve are required in order to permit complete closure.